U.S. patent number 10,000,970 [Application Number 14/650,100] was granted by the patent office on 2018-06-19 for downhole drilling assembly with motor powered hammer and method of using same.
This patent grant is currently assigned to NATIONAL OILWELL DHT, L.P.. The grantee listed for this patent is National Oilwell DHT, L.P.. Invention is credited to Alan Martyn Eddison, Alastair Henry Walter Macfarlane, Rory McCrae Tulloch.
United States Patent |
10,000,970 |
Tulloch , et al. |
June 19, 2018 |
Downhole drilling assembly with motor powered hammer and method of
using same
Abstract
A drilling assembly assembly includes a hammer motor, a shaft, a
driver, and a hammer (218). The shaft is operatively connectable to
the hammer motor and rotated thereby. The driver is operatively
connectable to the shaft, and includes a cam (such as guide channel
232) rotatable with the shaft and a fixed guide (such as guide pins
230) having a guide surface thereon. The cam is engageable with the
guide surface and axially movable thereabout during rotation
thereof. The hammer is operatively connectable to the driver and
axially movable therewith, axially movable within the housing (215)
independently from axial movement of the housing, and engageable
with the bit to impart an impact thereto whereby the bit is
hammered.
Inventors: |
Tulloch; Rory McCrae (Aberdeen,
GB), Eddison; Alan Martyn (York, GB),
Macfarlane; Alastair Henry Walter (Angus, GB) |
Applicant: |
Name |
City |
State |
Country |
Type |
National Oilwell DHT, L.P. |
Houston |
TX |
US |
|
|
Assignee: |
NATIONAL OILWELL DHT, L.P.
(Houston, TX)
|
Family
ID: |
50884144 |
Appl.
No.: |
14/650,100 |
Filed: |
December 6, 2013 |
PCT
Filed: |
December 06, 2013 |
PCT No.: |
PCT/US2013/073619 |
371(c)(1),(2),(4) Date: |
June 05, 2015 |
PCT
Pub. No.: |
WO2014/089457 |
PCT
Pub. Date: |
June 12, 2014 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20150315846 A1 |
Nov 5, 2015 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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61734853 |
Dec 7, 2012 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B
4/10 (20130101); E21B 4/20 (20130101); E21B
4/14 (20130101); C09J 183/04 (20130101); C08L
9/02 (20130101); E21B 4/003 (20130101); E21B
1/02 (20130101) |
Current International
Class: |
E21B
4/14 (20060101); E21B 4/20 (20060101); E21B
1/02 (20060101); E21B 4/00 (20060101); C08L
9/02 (20060101); E21B 4/10 (20060101); C09J
183/04 (20060101) |
Field of
Search: |
;175/57 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Canadian Patent Application No. 2,894,163 Office Action dated May
11, 2016 (4 pages). cited by applicant .
Canadian Patent Application No. 2,894,163 Office Action dated Feb.
7, 2017 (4 pages). cited by applicant .
PCT/US2013/073619 International Search Report and Written Opinion
dated Apr. 1, 2015, 14 pages. cited by applicant .
PCT/US2013/073619 International Preliminary Report on Patentability
dated Jun. 18, 2015, 11 pages. cited by applicant .
Canadian Patent Application No. 2,894,163 Office Action dated Nov.
27, 2017 (3 pages). cited by applicant.
|
Primary Examiner: Bemko; Taras P
Attorney, Agent or Firm: Conley Rose, P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a national phase application of PCT Application
No. PCT/US2012/053004 which claims the benefit of to U.S.
Provisional Application No. 61/734,853 filed on Dec. 7, 2012, the
entire contents of which are hereby incorporated by reference.
Claims
What is claimed is:
1. A drilling assembly of a downhole drilling tool for drilling a
wellbore penetrating a subterranean formation, the downhole
drilling tool driven by surface equipment and comprising a drill
string, a bottom hole assembly, and a drill bit, the drilling
assembly comprising: a housing positionable about the bottom hole
assembly; a hammer motor positionable in the housing and
rotationally driven by fluid flow therethrough; a shaft operatively
connectable to the hammer motor and rotatably thereby; a driver
operatively connectable to the shaft, the driver comprising a cam
rotatable with the shaft and a guide having a guide surface
thereon, the cam engageable with the guide surface and axially
movable thereabout during rotation thereof; a hammer operatively
connectable to the driver and axially movable therewith, the hammer
axially movable within the housing independently from axial
movement of the housing, the hammer engageable with the bit to
impart an impact thereto whereby the bit is hammered; and a fluid
passage extending through the drillstring, through the hammer, and
through the bit, the fluid passage including a flow restriction
positioned to restrict flow of fluid through the hammer and directs
an axially-downward fluid force against the hammer when fluid flows
through the flow restriction; wherein the flow restriction is
coupled for movement with the hammer and is axially movable
relative to the drill bit.
2. The drilling assembly of claim 1, wherein the flow restriction
is a nozzle having an axially extending flow path, the nozzle
positionable in the housing to selectively restrict flow of fluid
through the fluid passage.
3. The drilling assembly of claim 2, wherein the nozzle is
positionable within the portion of the passage extending through
the hammer.
4. The drilling assembly of claim 1, wherein the hammer motor
comprises a helical stator with a helical rotor rotatable
therein.
5. The drilling assembly of claim 4, wherein the helical rotor is
solid.
6. The drilling assembly of claim 4, wherein the helical rotor is
hollow to permit fluid flow therethrough.
7. The drilling assembly of claim 1, wherein the hammer motor
comprises a helical rotor with a helical stator rotatable
therein.
8. The drilling assembly of claim 1, wherein the flow restriction
is a nozzle having an axially extending flow path, the nozzle being
disposed within the hammer at the entry of the portion of the
passage extending through the hammer.
9. The drilling assembly of claim 1, wherein the shaft comprises a
flexible shaft.
10. The drilling assembly of claim 1, further comprising an adapter
operatively connecting the shaft to the driver.
11. The drilling assembly of claim 1, wherein the driver has
splines engageable with splines on the hammer; and wherein the
drill bit is mounted to the housing such that rotation and axial
movement of the bit relative to the housing are prevented.
12. The drilling assembly of claim 1 wherein the cam comprises
guide pins and the guide surface comprises a guide channel; and
wherein the guide channel faces axially; and wherein the guide pins
extend radially and comprise bearings, configured to roll on the
guide channel.
13. The drilling assembly of claim 1, wherein the cam comprises
guide pins and the guide surface comprises a guide channel, the
guide pins slidably positionable in the guide channel.
14. The drilling assembly of claim 1, wherein the cam comprises a
floating guide ring having a cam surface and the guide surface
comprises a guide ring engageable, the guide ring having the guide
surface thereon.
15. The drilling assembly of claim 1, wherein the cam is positioned
about an end of the hammer.
16. The drilling assembly of claim 1, wherein the hammer comprises
a bit adapter operatively connectable to the bit and wherein the
guide surface is positioned about an end of the bit adapter.
17. The drilling assembly of claim 1, further comprising a
universal joint operatively connectable to the motor and the shaft;
and wherein the hammer is configured to move independently of
weight on bit applied to the housing from a surface unit.
18. The drilling assembly of claim 1, wherein the hammer comprises
a shaft adapter operatively connectable to the shaft and a bit
adapter operatively connectable to the bit, the cam surface
positionable about the shaft adapter and the guide surface
positionable about the bit adapter.
19. The drilling assembly of claim 1, wherein the housing having
splines engageable with splines on the bit.
20. A drilling assembly of a downhole drilling tool for drilling a
wellbore penetrating a subterranean formation, the downhole
drilling tool driven by surface equipment and comprising a drill
string, a bottom hole assembly, and a drill bit, the drilling
assembly comprising: a housing positionable about the bottom hole
assembly; a hammer motor positionable in the housing and
rotationally driven by fluid flow therethrough; a shaft operatively
connectable to the hammer motor and rotatably thereby; a driver
operatively connectable to the shaft, the driver comprising a cam
rotatable with the shaft and a guide having a guide surface
thereon, the cam engageable with the guide surface and axially
movable thereabout during rotation thereof; a hammer operatively
connectable to the driver and axially movable therewith, the hammer
axially movable within the housing independently from axial
movement of the housing, the hammer engageable with the bit to
impart an impact thereto whereby the bit is hammered; and a fluid
passage extending through the drill string, through the hammer, and
through the bit, the fluid passage including a flow restriction
positioned to restrict flow of fluid through the hammer and
configured such that an axially-downward force is applied to the
hammer by the fluid when fluid flows through the flow restriction;
wherein the flow restriction is a nozzle; wherein the flow passage
is configured to allow a total flow rate of drilling fluid to enter
the drill string, and to allow a first portion of the total flow
rate to flow through the hammer into the bit; and wherein the fluid
passage includes a bypass passage extending through the sidewall of
the hammer and configured to allow a second portion of the total
flow rate to contact a bearing disposed around the hammer,
supporting the hammer in the housing.
21. The drilling assembly of claim 20, wherein the second portion
of the total flow rate is from 5 to 15 percent of the total flow
rate.
22. A drilling system for drilling a wellbore penetrating a
subterranean formation, comprising: a downhole tool comprising a
bottom hole assembly, a drill string, and a drill bit deployable by
a surface system; and a drilling assembly, comprising: a housing
positionable about the bottom hole assembly; a hammer motor
positionable in the housing and rotationally driven by fluid flow
therethrough; a shaft operatively connectable to the hammer motor
and rotatably thereby; a driver operatively connectable to the
shaft, the driver comprising a cam rotatable with the shaft and a
fixed guide having a guide surface thereon, the cam engageable with
the guide surface and axially movable thereabout during rotation
thereof; a hammer operatively connectable to the driver and axially
movable therewith, the hammer axially movable within the housing
independently from axial movement of the housing, the hammer
engageable with the bit to impart an impact thereto whereby the bit
is hammered; wherein the drill bit is threadably mounted to the
housing, the threaded mounting preventing the bit from moving
independently of the housing; and a flow restriction coupled for
movement with the hammer, the flow restriction receives at least a
portion of the fluid flow and to generate an axially-downward fluid
force against the hammer to drive the hammer downward; wherein the
flow restriction is axially movable relative to the drill bit.
23. The drilling system of claim 22, further comprising a fluid
passage extending through the drillstring, through the bottom hole
assembly, through the hammer, and through the bit, the fluid
passage including a nozzle positioned to restrict flow of fluid
through the hammer, the nozzle configured such that an axial force
is applied to the hammer when fluid flows through the fluid
passage.
24. The drilling system of claim 22, further comprising a downhole
motor, the drilling assembly rotationally driven by the downhole
motor.
25. A method of drilling a wellbore penetrating a subterranean
formation, the method comprising: deploying a downhole tool into
the subterranean formation via a surface system, the downhole tool
comprising a bottom hole assembly, a drill string, and a drill bit;
rotating a drilling assembly comprising a hammer motor, a shaft
operatively connectable to the hammer motor, a driver operatively
connectable to the shaft, and a hammer, the driver comprising a cam
and a fixed guide having a guide surface thereon, the hammer
operatively connectable to the driver and axially movable
therewith; rotating the cam with the shaft by passing a fluid
through the hammer motor; and hammering the bit with the hammer by
engaging the guide surface with the cam such that the cam is
axially moved about the guide surface during the rotating and the
hammer is axially moved within a housing independently from axial
movement of the housing; wherein hammering the bit includes
generating an axially-downward fluid force to drive the hammer
downward by passing the fluid through a flow restriction that is
coupled for movement with the hammer and is axially movable
relative to the drill bit.
26. The method of claim 25, further comprising selectively
increasing pressure in the drilling assembly by selectively
restricting flow therethrough.
27. The method of claim 25, wherein the hammering comprises
slidably positioning pins of the cam about a guide channel of the
guide surface.
28. The method of claim 25, wherein the hammering comprises
slidably engaging a cam surface of the cam along the guide
surface.
29. The method of claim 25, further comprising passing a portion of
the fluid through a rotor of the hammer motor.
30. The method of claim 25, wherein generating an axially-downward
force to drive the hammer comprises selectively restricting the
flow of fluid through the hammer.
Description
BACKGROUND
This present disclosure relates generally to techniques for
performing wellsite operations. More specifically, the present
disclosure relates to techniques, such as hammers, for drilling
wellbores.
Oilfield operations may be performed to locate and gather valuable
downhole fluids. Oil rigs are positioned at wellsites, and downhole
equipment, such as drilling tools, are deployed into the ground by
a drill string to reach subsurface reservoirs. At the surface, an
oil rig is provided to deploy stands of the pipe into the wellbore
to form the drill string. Various surface equipment, such as a top
drive, or a Kelly and a rotating table, may be used to apply torque
to the stands of pipe, to threadedly connect the stands of pipe
together, and to rotate the drill bit. A drill bit is mounted on
the lower end of the drill string, and advanced into the earth by
the surface equipment to form a wellbore.
The drill string may be provided with various downhole components,
such as a bottom hole assembly (BHA), drilling motor, measurement
while drilling, logging while drilling, telemetry and other
downhole tools, to perform various downhole operations. The
drilling motor may be provided to drive the drill bit and advance
the drill bit into the earth. Examples of drilling motors are
provided in U.S. Pat. Nos. 7,419,018, 7,461,706, 6,439,318,
6,431,294, 2007/0181340, and 2011/0031020.
SUMMARY
In at least one aspect, the disclosure relates to a drilling
assembly of a downhole drilling tool for drilling a wellbore
penetrating a subterranean formation. The downhole drilling tool is
driven by surface equipment and includes a drill string, a bottom
hole assembly, and a drill bit. The drilling assembly includes a
hammer motor positionable about the bottom hole assembly and
rotationally driven by fluid flow therethrough, a shaft operatively
connectable to the hammer motor and rotatably thereby, a driver
operatively connectable to the shaft, and a driver including a cam
rotatable with the shaft and a fixed guide having a guide surface
thereon. The cam is engageable with the guide surface and axially
movable thereabout during rotation thereof. The hammer is
operatively connectable to the driver and axially movable
therewith, axially movable within the housing independently from
axial movement of the housing, and engageable with the bit to
impart an impact thereto whereby the bit is hammered.
The drilling assembly may include a nozzle positionable in the
housing to selectively restrict flow of fluid therethrough. The
hammer may have a passage therethrough, and the nozzle may be
positionable about the passage to selectively restrict the flow
therethrough whereby force is applied to the hammer. The hammer
motor may include a helical stator with a helical rotor rotatable
therein, a helical rotor with a helical stator rotatable therein,
and/or joints, motor shafts, and/or bearings. The helical rotor may
be solid, or hollow to permit fluid flow therethrough.
The drilling assembly may also include flow restrictors. The shaft
may include a flexible shaft. The drilling assembly may also
include an adapter operatively connecting the shaft to the driver.
The driver or housing may have splines engageable with splines on
the hammer or bit. The drilling assembly may also include bearings
operatively connectable to the hammer.
The cam may include guide pins and the guide surface may have a
guide channel. The guide pins may be slidably positionable in the
guide channel. The cam may include a floating guide ring having a
cam surface and the guide surface may include a fixed guide ring
engageable. The fixed guide ring may have the guide surface
thereon. The cam may be positioned about one an end of the hammer
and wherein the guide surface is positioned about an end of the bit
or a bit adapter.
The drilling assembly may also include a universal joint
operatively connectable to the motor and the shaft. The hammer may
include a shaft adapter operatively connectable to the shaft and a
bit adapter operatively connectable to the bit. The cam surface may
be positionable about the shaft adapter and the guide surface
positionable about the bit adapter. The drilling assembly may
include a housing having splines engageable with splines on the
bit.
In another aspect, the disclosure relates to a drilling system for
drilling a wellbore penetrating a subterranean formation. The
drilling system includes a downhole tool and a drilling assembly.
The downhole tool includes a bottom hole assembly, a drill string,
and a drill bit deployable by a surface system. The drilling
assembly includes a hammer motor positionable about the bottom hole
assembly and rotationally driven by fluid flow therethrough, a
shaft operatively connectable to the hammer motor and rotatably
thereby, a driver operatively connectable to the shaft, and a
hammer. The driver includes a cam rotatable with the shaft and a
fixed guide having a guide surface thereon. The cam is engageable
with the guide surface and axially movable thereabout during
rotation thereof. The hammer is operatively connectable to the
driver and axially movable therewith, axially movable within the
housing independently from axial movement of the housing, and
engageable with the bit to impart an impact thereto whereby the bit
is hammered.
The drilling assembly may be rotationally driven by the surface
system. The drilling system also includes a downhole motor. The
drilling assembly may be rotationally driven by the downhole
motor.
Finally, in another aspect, the disclosure relates to a method of
drilling a wellbore penetrating a subterranean formation. The
method involves deploying a downhole tool into the subterranean
formation via a surface system. The downhole tool includes a bottom
hole assembly, a drill string, and a drill bit. The method also
involves rotating a drilling assembly including a hammer motor, a
shaft operatively connectable to the hammer motor, a driver
operatively connectable to the shaft, and a hammer. The driver
includes a cam and a fixed guide having a guide surface thereon,
and is operatively connectable to the driver and axially movable
therewith. The method also involves rotating the cam with the shaft
by passing a fluid through the hammer motor, and hammering the bit
with the hammer by engaging the guide surface with the cam such
that the cam is axially moved about the guide surface during the
rotating and the hammer is axially moved within the housing
independently from axial movement of the housing.
The method may also involve selectively increasing pressure in the
drilling assembly by selectively restricting flow therethrough. The
hammering may involve slidably positioning pins of the cam about a
guide channel of the guide surface, and/or slidably engaging a cam
surface of the cam along the guide surface. The method may also
involve passing a portion of the fluid through a rotor of the
hammer motor and/or applying force to drive the hammer by
selectively restricting the flow of fluid through the hammer.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the present disclosure can be understood in detail, a more
particular description of the disclosure is illustrated in the
appended drawings. It is to be noted, however, that the appended
drawings illustrate only example embodiments and are, therefore,
not to be considered limiting of its scope. The figures are not
necessarily to scale and certain features, and certain views of the
figures may be shown exaggerated in scale or in schematic in the
interest of clarity and conciseness.
FIG. 1 depicts schematic views, partially in cross-section of a
wellsite having a surface system and a downhole drilling system for
drilling a wellbore, the downhole drilling system having a downhole
drilling assembly with a motor powered hammer.
FIGS. 2A-2C, 3, 4A-4B, 5, and 6 depict various views of portions of
a downhole drilling assembly with motor powered hammer with a guide
pin.
FIGS. 7-8 depict various views of a downhole drilling assembly with
motor powered hammer with wave profile cam.
FIGS. 9-12 depict various views of a downhole drilling assembly
with motor powered hammer with bit cam.
FIGS. 13-20 depict various views of a downhole drilling assembly
with motor powered hammer with another bit cam.
FIGS. 21A-21B, 22A-22B, 23, and 24 depict various views of a
downhole drilling assembly with motor powered hammer with a
rotating stator and a non-rotating, solid rotor.
FIGS. 25A-25B, 26, 27, and 28 depict various views of a downhole
drilling assembly with motor powered hammer with a rotating stator
and a non-rotating, hollow rotor.
FIG. 29 is a flow chart depicting a method of drilling a
wellbore.
DETAILED DESCRIPTION OF THE INVENTION
The description that follows includes exemplary apparatus, methods,
techniques, and/or instruction sequences that embody techniques of
the present subject matter. However, it is understood that the
described embodiments may be practiced without these specific
details.
The present disclosure relates to downhole drilling assemblies with
motor powered hammers and drill bits used in drilling wellbores.
The drill bit may be rotated by rotation of the drill string from
the surface or by a drill bit rotation drilling motor. A motor
powered hammer may be used to generate rotational output that is
converted to axial reciprocation, thereby providing a reciprocating
action to hammer the drill bit. The reciprocating action of the
hammer may move independently of a housing and independent of
weight on bit that is applied to the housing.
The motor powered hammer may operate without requiring an
oscillating type design using a variable orifice (e.g., valve
block) to redirect and/or restrict flow. Flow rate of fluid flowing
through the downhole drilling assembly may be configured to
selectively adjust the operation of the drilling motors and/or
rotation of the drill bit. Independent control of bit rotational
speed and/or weight on bit from hammer impact speed may be provided
with bit rotation by surface equipment (without requiring a second,
bit rotation motor). Hydraulic motors may be used to increase
speed, for example, by increasing flow rate. Independent control
may also be provided by using a bit rotation motor that is
electrically powered.
In given embodiments of these motor-powered hammer designs, the
motor is used solely to provide rotational speed and torque to
create axial reciprocation of a hammer mass. High hydraulic
pressure drop through the hammer shaft nozzle can thus be used to
create large downward hammer force over the available annular
thrust area as the motor torque available may be used solely to
pull the hammer shaft upwards with the hydraulic pressure pushing
it downwards to create the impact on the bit. No torque from the
hammer motor is used to drill the bit rotationally.
The hammer may be coupled to the motor (stator or rotor) and
rotates in the hammer tool housing as a response of fluid flow in
the motor. The hammer may have a cam surface to gradually lift the
hammer as it rotates. The hammer may also reciprocate in the hammer
tool housing (either the stator or the rotor also reciprocates, or
there is a splined connection between the motor and the hammer).
The hammer may have a flow passage restricted by a nozzle to
provide a controllable down thrust force. The hammer may impact the
bit (directly or indirectly). Rotation between the bit and the
hammer tool housing may be prevented (by a threaded connection or a
splined connection).
FIG. 1 depicts an example environment in which a downhole drilling
assembly may be used. While a land-based drilling rig with a
specific configuration is depicted, the drilling assembly herein
may be usable with a variety of land based or offshore
applications. In each version, a drilling system 100 includes a rig
101 positionable at a wellsite 102 for performing various wellbore
operations, such as drilling. The drilling system 100 may have a
steerable assembly, or a straight-hole hammer drilling assembly
that is not steerable. The drilling system 100 may be used, for
example, with coil tubing applications with two motors.
FIG. 1 depicts a schematic view, partially in cross-section, of the
wellsite 102. The drilling system 100 also includes a drill string
103 with a bottom hole assembly (BHA) 108 and a drill bit 104 at an
end thereof. The drill string 103 may include drill pipe, drill
collars, coiled tubing or other tubing used in drilling operations.
The drill bit 104 is advanced into a subterranean formation 105 to
form a wellbore 106. The bit 104 may be, for example, a roller cone
or polycrystalline diamond cutter (PDC) bit.
Various surface (or rig) equipment 107, such as a Kelly, rotary
table, top drive, elevator, etc., may be provided at the rig 101 to
rotate the drill bit 104. A surface controller 112a is also
provided at the surface to operate the drilling system. Downhole
equipment, such as the BHA 108, is deployed from the surface
equipment and into the wellbore 106 by the drill string 103 to
perform downhole operations.
The BHA 108 is at a lower end of the drill string 103 and contains
various downhole equipment for performing downhole operations. Such
equipment may include, for example, measurement while drilling,
logging while drilling, telemetry, processors and/or other downhole
tools. As shown, the BHA 108 includes a downhole controller 112b
for communication between the BHA 108 and the surface controller
112a. One or more controllers 112a,b may be provided. The BHA 108
may also be provided with various motors (e.g., one or two motors)
for operating downhole equipment, such as the drill bit 104.
The BHA 108 may have a motor powered hammer 111 for hammering the
drill bit 104. The motor powered hammer 111 is positioned between
the drill string 103 and the drill bit 104. The motor powered
hammer 111 may be positioned, for example, adjacent or as part of
the BHA 108. Optionally, the BHA 108 may also include a drill bit
drill bit rotation motor 109 that may be used to rotationally drive
the drill bit. As shown, the drill bit rotation motor 109 may be
located uphole from the motor powered hammer 111. The drill bit
rotation motor 109 and/or the rig equipment 107 may be used to
rotate the bit 104. For example, the drill bit 104 may be driven
from the surface equipment (e.g., top drive or rotary table at the
surface) or from the drill bit rotation motor 109 that drives the
motor powered hammer 111, with the stator of the motor powered
hammer 111 screwed into the bit box of the drill bit rotation motor
109 above it.
The motor powered hammer 111 may include, for example, an electric,
vane, turbodrill, moineau or other motor for connection to and/or
to hammer the drill bit 104. An example of a moineau motor that may
be usable is provided in U.S. Pat. No. 7,419,018. In some cases,
the motor powered hammer 111 may include a designed motor using,
for example, helical rotor and stator combinations. The motor
powered hammer 111 may be, for example, about a 4.75 inch (12.06
cm) motor with about 250 to about 300 gpm (about 946.35 to about
1135.6 l/min) through its helical profile. The drill bit rotation
motor 109 may be, for example, an electric, vane, turbo drill,
moineau or other motor capable of providing rotation to the
bit.
A mud pit 110 may be provided at the surface for passing mud
through the drill string 103, the BHA 108 and out the bit 104 as
indicated by the arrows. The drill bit rotation motor 109 and the
motor powered hammer 111 may be activated by fluid flow from the
mud pit 110 and through the drill string 103. Flow of drilling mud
from pit 110 may be used to activate the drilling motors during
drilling, for example by rotationally driving the motors or other
downhole components.
The rotational speed of the bit 104 may be selectively varied as
desired, for example, using the surface rig equipment 107, or with,
for example, an electric drill bit rotation motor 109. For example,
rotation of the surface rig equipment 107 can be varied to drive
the bit, while fluid flow through the BHA 108 may be used to vary
the reciprocation speed of the motor powered hammer 111. When, for
example, a hydraulic drill bit rotation motor 109 is used, the
rotational speed of the bit may also be varied by flow
therethrough. The flow through the BHA 108 may vary both the
rotational speed of the bit using the drill bit rotation motor 109
and speed of the motor powered hammer 111. The motor powered hammer
111 may be operated independently of, or cooperatively with, other
equipment, such as the drill bit rotation motor 109.
FIGS. 2A-8 depict various views of a downhole drilling assembly
with a motor powered hammer reciprocated by a rotationally driven
splined driver. FIGS. 2A-6 depict a first version of the motor
powered hammer with a guide pin configuration. FIGS. 7 and 8 depict
a second version of the motor powered hammer with a cam
configuration. These configurations may be formed, for example,
from a standard drilling motor provided with a bearing casing
having an additional external pin thread, a reduced diameter bit
box on the output shaft, and a special output shaft adapter with a
splined connection.
FIGS. 2A-6 show various views of an example of a downhole drilling
assembly 200 usable, for example, in the drilling system 100 of
FIG. 1. As shown in FIG. 2A, the drilling assembly 200 has a stator
housing 215, a hammer motor 211, an output shaft adapter 216, a
spline driver 224, a hammer 218 and a bit 204. FIGS. 2B-6 show
detailed views of various portions of the drilling assembly 200 of
FIG. 2A.
FIG. 2B shows the hammer motor 211 in greater detail. The hammer
motor 211 may be a conventional drilling motor, such as those
described herein. Small modifications may be made to the lower end
of the hammer motor 211 (i.e. outer bearing, casing, bit box and/or
output shaft). Fluid passes through the drilling assembly 200 to
rotationally drive the hammer motor 211. The hammer motor 211 has a
rotor 220 rotationally driven within a stator 222 as fluid flows
therethrough. The hammer motor 211 may also be provided with joints
212 (e.g., universal joints), motor shafts 217a,b, bearings 219 and
other features. Motor shafts 217a,b as shown include a flexible
shaft 217a and an output shaft 217b.
As shown in FIGS. 2A-2C, fluid passes through the hammer motor 211,
through the output shaft adapter 216 and hammer 218, and out the
bit 204. Flow restrictors 225 (e.g., journal or other bearings) may
optionally be inserted about the drilling assembly 200 to provide,
for example, about 0.010 to about 0.020 inches (2.54 to 5.08 mm)
clearance. Coating (e.g., tungsten carbide coating) may optionally
be applied about the drilling assembly 200 to prevent wear due to,
for example, fluid flow therethrough.
As shown in FIGS. 2C and 3, a nozzle 223 may also be provided to
selectively restrict flow through the downhole drilling assembly
200. The nozzle 223 may be used to increase the pressure drop and
increase thrust of the hammer. For example, the flow may be
restricted with the nozzle 223 to increase downward thrust force of
the hammer 218. In an example, the nozzle 223 may be a valve (e.g.,
vent valve) rotatably or axially positionable about the housing 220
by movement of the output shaft 216 to selectively restrict a flow
path therethrough.
The output shaft adapter 216 extends downhole from a downhole end
of the out shaft 217b. The output shaft adapter 216 is connected to
the spline drive 224. The spline drive 224 has internal drive
splines 226 on an inner surface thereof. The inner drive splines
226 are engageable with corresponding outer splines 228 on the
hammer 218 for rotation therewith as shown in FIG. 5. As the output
shaft adapter 216 rotates with hammer motor 211, the spline drive
224 and hammer 218 rotate therewith. Bearings 225 (e.g., radial
bearings) may be provided to support the hammer 218 in the housing
215 during operation.
As shown in FIGS. 3-5, guide pins 230 extend through the housing
215 and into a guide channel 232 on an outer surface of the hammer
218. As shown, three guide pins 230 are provided about the hammer
218, but a desired number (e.g., from about 1 to about 6 guide pins
230) may be provided to facilitate operation thereof. The guide
pins 230 may be rotationally supported in the guide channel 232 by
bearings, such as journal bearings 231a as shown in FIG. 4A and/or
ball bearings 231b as in FIG. 4B. The guide pins 230 may be
provided with a bearing assembly with the bearings 231a,b mounted
therearound to support the guide pins 230 for rotation and wear
prevention.
The guide channel 232 slidingly receives the guide pins 230 as the
hammer 218 rotates within the housing 215. The guide channel 232
has a wave pattern (FIG. 5) with peaks and valleys to define a path
for movement of the guide pins 230 therealong. The wave (or
undulating or helical) guide channel 232 may act as a gear box to
convert motor rotation into axial reciprocation of the hammer. The
guide channel 232 design may be, for example, a shallow sine wave
(or undulating) profile helix. Impact may be diverted away from the
guide pins 230 by providing milled cut-outs at a downhole end of
the wave pattern. The wave pattern may be configured to prevent the
guide pins 230 from bottoming out on the tops of the milled
undulating profile and/or to prevent potential wear, bending and/or
deformation of the guide pins 230 and the guide channel 232 as they
are subject to loading. In the examples shown with three guide pins
230, the hammer 218 impacts three times per rotation. The number of
impacts may be adjusted by the number of guide pins and the shape
of the guide channel 232. Axial speed of the hammer 218 can be
calculated based on the wave profile of the guide channel 232 that
is provided and the speed of rotating the hammer motor 218.
The shape of the guide channel 232 may be configured to allow the
hammer 218 to move axially back and forth in a reciprocating
pattern as the hammer 218 rotates within the housing 215. The
hammer 218 may move axially within the housing 215 and independent
of axial movement of the housing 215. The hammer 218 may be movable
within the housing 215 such that the hammer is independent of
weight on bit applied to the housing 215 from the surface.
As the hammer 218 reaches a downhole portion of the guide channel
232 and `bottoms out,` the hammer head 227 contacts the bit 204 as
indicated by the arrow in FIG. 6. When at a bottom of the wave
profile, the hammer action may be used to provide a small
force/high frequency impact to the bit 104. As the hammer 218 moves
along the wave pattern to an uphole position, the hammer head 227
retracts a distance from the bit 204. A downhole end of the hammer
head 227 and an uphole end of the bit 204 may have corresponding
large flat circular surfaces for shock absorption and wear
prevention. Optionally, the hammer head 227 may be provided with,
for example, splayed and swaged metal or inserts to prevent
wear.
A mass force of the hammer 218 at impact may be calculated, with
the force being equal to a pressure drop across the flow area
(e.g., at the nozzle 223) times the area between a flow restrictor,
such as radial bearing 225 diameter) and the flow area at the
nozzle 223. Bypass flow may cool the flow restrictors 225 which
pass through holes above the guide pins 230 in the hammer 218, for
example where a sealed bearing output shaft motor is used. Bypass
leakage may be from about 5 to about 15 percent of total flow rate
through the downhole drilling assembly 200, but with about 100% of
the flow exiting nozzles in the bit 204. Flow through the drilling
assembly 200 and/or the drilling motor 211 may be configured as
shown, for example, in FIG. 1.
The bits as used herein may be connected to the housing of the
drilling assembly 200, for example, by a threaded joint, a splined
or a flexible bellows connection. As shown, for example, in FIGS.
2-13, the threaded joint connection may be used, for example, which
will result in the outer casing to at least partially absorb forces
on the drilling assembly as the hammer moves between a non-contact
position and a contact position about the bit. The forces may be
absorbed to reduce the force on the bit. For the splined connection
or flexible bellows at the bit (as shown for example in FIGS.
21-28) the full hammer force may be transferred to provide more
force on the bit. A threaded connection may also absorb some of the
hammer input. Sealing may be needed for the various connections,
such as the splined connection. The flexible bellows connection may
provide an intermediate design, for example, to eliminate the need
for dynamic sealing as may be needed with a splined connection.
FIGS. 7-8 show various views of an example of a drilling assembly
700 with a hammer motor 711 usable, for example, in the drilling
system 100 of FIG. 1. The drilling assembly 700 has a housing 715,
the hammer motor 711, an output shaft adapter 716, a spline drive
724, a hammer 718 and a bit 704. The hammer motor 711 may employ,
for example, the hammer motor 211 of FIGS. 2A-6 having a rotor
rotationally driven within a stator as fluid flows therethrough.
The hammer motor 711 may also employ other components similar to
the hammer motor 211, such as nozzle 723.
The hammer motor 711 is coupled to the output shaft adapter 716.
The output shaft adapter 716 is connected to the spline drive 724
and rotates therewith. Flow Restrictors 725 (e.g., radial bearings)
are provided to support the hammer 718 in the housing 715. A
rotating guide ring 730 is positioned on the spline drive 724 and
rotates therewith. Spacers 735 may optionally be provided adjacent
the flow restrictors 725. The spline drive 724 has drive splines
726 engageable with corresponding guide splines 728 on the rotating
guide ring 730 for rotation therewith.
The rotating guide ring 730 is movably positionable adjacent a
fixed guide ring 732. The rotating guide ring 730 and the fixed
guide ring 732 have mated cam surfaces 733a,b thereon for cam
interaction therebetween. The fixed guide ring 732 slidingly
receives the rotating guide ring 730 as the rotating guide ring 730
is rotated by output shaft adapter 716 within the housing 715. As
shown, the cam surfaces 733a,b each have a corresponding undulating
wave pattern to define a path for movement of the rotating guide
ring 730 along the fixed guide ring 732. The cam surface 733a of
the rotating guide ring 730 moves between a fully aligned position
and a non-aligned position along the cam surface 733b of the fixed
guide ring 732 as the rotating guide ring 730 rotates relative
thereto.
The shape of the wave profile defined by the mated cam surfaces
733a,b may have a similar helical shape to the guide channel 232 of
FIGS. 3-6 for providing similar reciprocation of the hammer 718.
The shape of the fixed guide ring 732 may be configured to receive
the rotating guide ring 730 and allow the hammer 718 to move
axially back and forth in a reciprocating pattern as the output
shaft adapter 716 rotates the rotating guide ring 730 within the
housing 715. As the rotating guide ring 730 moves between the
aligned and non-aligned positions, the hammer 718 is axially
reciprocated back and forth. The hammer 718 has a hammer head 727
extending therefrom for contact with the bit 704. In the aligned
position, the rotating guide ring 730 `bottoms out` and the hammer
718 impacts the bit 704. The hammer 718 is retracted a distance
from the bit as the rotating guide ring 730 moves to a non-aligned
(or uphole) position.
The hammer impacts may be configured to avoid absorption by the cam
surfaces 733a,b. Axial thrust may be taken by flat, horizontal
portion of the cam surfaces 733b on the top of the bit 704. The cam
surfaces 733a,b act to create reciprocation. The cam surfaces
733a,b may be provided with replaceable inserts to prevent wear.
The inserts may be threaded into the hammer 718 and/or bit 704.
As in FIGS. 2A-6, the number of cam peaks and valleys may be
selected to provide a desired reciprocation. For example, if using
four cams then the reciprocation of the hammer 718 will be for
times the rotational speed and the axial speed of the hammer 718
can be calculated. In another example, one cam may be used to give
longer life with maximum contact area. The hammer mass force of
impact may also be calculated, with the force being equal to the
pressure drop across the nozzle 723 times the area between the flow
restrictor/radial bearing diameter and the bore of the nozzle.
FIGS. 9-20 depict various configurations of a motor powered hammer
with a bit cam. FIGS. 9-12 depict a motor powered hammer with a bit
cam and standard motor configuration. FIGS. 13-20 depict a motor
powered hammer with a bit cam and a special motor
configuration.
FIGS. 9-12 show various views of an example of a drilling assembly
900 with a hammer motor 911 usable, for example, in the drilling
system 100 of FIG. 1. This version is similar to the bearing
section of FIGS. 2A-8. The hammer motor 911 may be, for example, a
standard Positive Displacement Motor (PDM) modified with a new
bearing casing with an additional external pin thread and a special
output shaft adapter with a splined connection.
The drilling assembly 900 of FIG. 9 has a housing 915, the hammer
motor 911, an output shaft adapter 916, spline drive 924, a hammer
918 and a bit 904. The hammer motor 911 has a rotor 920
rotationally driven within a stator 922 as fluid flows
therethrough. A nozzle 923 may also be provided to selectively
restrict flow through the downhole drilling assembly 900. As shown,
two nozzles are provides, one at the top of the rotor 920 and
another uphole of hammer 918.
As shown in FIGS. 9 and 10, the hammer motor 911 has flexible shaft
917a and output shaft 917b coupled by threaded connections 912. The
downhole motor shaft 917 is coupled to the output shaft adapter
916. The output shaft adapter 916 is connected to the spline drive
924. The spline drive 924 has drive splines 926 on an outer surface
thereof engageable with corresponding hammer splines 928 on an
inner surface of the hammer 918. As the output shaft adapter 916
rotates with hammer motor 911, the spline drive 924 and hammer 918
rotate therewith. Bearings 925 (e.g., radial bearings) are provided
to support the hammer 918 in the housing 915.
As shown in FIGS. 11 and 12, the hammer 918 has a hammer head 927
extending therefrom for contact with the bit 904. A downhole end of
the hammer head 927 has a wave pattern therealong defining a cam
surface 933a. An uphole end of the bit 904 has a corresponding wave
pattern therealong defining a mated cam surface 933b for receiving
the cam surface 933a. In the aligned position, the rotating hammer
head 1927 `bottoms out` and the hammer 918 impacts the bit 904. The
hammer 918 is retracted a distance from the bit as the cam surface
933a rides up along cam surface 933b to an uphole position.
Cam surfaces 933a,b may have a cam pattern similar to the wave
profile to that of FIGS. 7-8 for providing the desired
reciprocation. As depicted, the wave pattern has an inclined edge
to permit the cam surface 933a to slide to the uphole position, and
a vertical drop off to permit the cam surface 933a to fall back to
a downhole position. The cam pattern defined by the cam surfaces
herein, such as the cam surfaces 933a,b, may be configured to allow
the hammer 918 to move axially back and forth in a reciprocating
pattern as the hammer 918 rotates within the housing 915. As the
hammer 918 reaches a downhole portion of the cam surfaces 933b and
`bottoms out,` the hammer head 927 is in full contact with the bit
904. As the hammer 918 moves along the cam pattern to an uphole
position, the hammer head 927 retracts a distance from the bit 904
and hammers the bit 904 as it returns to the bottomed out position.
As the hammer 918 moves to the bottom position, the hammer 918
impacts the bit 904, thereby providing percussive impact.
FIGS. 13-20 depict a motor powered hammer with a bit cam and
special motor configuration. This version as depicted has no thrust
bearings in the hammer motor. The motor may be a special PDM
configuration that provides a flexible shaft below the rotor. The
configuration may be used, for example, to eliminate the
requirement of having axial bearings and/or u-joints inside the
downhole drilling assembly, to reduce the number of moving
parts.
FIGS. 13-20 show various views of an example of a drilling assembly
1300 with a hammer motor 1311 usable, for example, in the drilling
system 100 of FIG. 1. The drilling assembly 1300 has a housing
1315, the hammer motor 1311, a flexible transmission shaft 1316, an
output shaft coupling 1324, a hammer 1318 and a bit 1304.
As shown in FIGS. 13-16, the hammer motor 1311 has a rotor 1320
rotationally driven within a stator 1322 as fluid flows
therethrough. A nozzle 1323 may also be provided increase the flow
rate which can be pumped past the rotor/stator.
The rotor 1320 has the flexible transmission shaft 1316 extending
downhole therefrom. The flexible transmission shaft 1316 is a
flexible shaft connected to a hammer 1318 by the output shaft
coupling 1324. The flexible transmission shaft 1316 may have taper
drives at each end thereof. The taper drives may be, for example,
1:10 or 1:20 Morse Tapers or threaded connections. The output shaft
coupling 1324 is connected the hammer 1318, and applies rotation
thereto. As the flexible transmission shaft 1316 rotates with
hammer motor 1311, the output shaft coupling 1324 and hammer 1318
rotate therewith.
Bearings (e.g., journal bearings) 1325 are provided to support the
hammer 1318 in the housing 1315, and act as flow restrictors to
control flow therethrough. The number of bearings 1325 may be
selected as desired. For example, one set, rather than three sets
as shown, may be used. Outer bearings (e.g., journal bearings) 1329
are positioned about the bearings 1325 and may be held in
compression by an over-sized adjusting ring 1331. Spacers 1335 may
also be provided between the bearings.
As shown in FIGS. 18-20, the hammer 1318 has a hammer head 1327
extending therefrom for contact with the bit 1304. A downhole end
of the hammer head 1327 has a cam pattern therealong defining cam
surface 1333a. An uphole end of the bit 1304 has a corresponding
cam pattern therealong defining mated cam surface 1333b for
receiving the cam surfaces 1333a. The cam surfaces 1333a,b may
operate similar to, for example, the cam surfaces 933a,b described
herein. In the aligned position, the hammer 1318 `bottoms out` and
the hammer head 1327 impacts the bit 1304. The hammer head 1327 is
retracted a distance from the bit 1304 as the cam surface 933a
rides up an incline of cam surface 933b to the uphole position.
The shape of the cam surfaces 1333a may be configured to allow the
hammer 1318 to move axially back and forth in a reciprocating
pattern as the hammer 1318 rotates within the housing 1315. As the
hammer 1318 `bottoms out,` the hammer head 1327 is in full contact
with the bit 1304. As the hammer 1318 moves along the cam pattern
to an uphole position, the hammer head 1327 retracts a distance
from the bit 1304 and hammers the bit 1304 as it returns to the
bottomed out position.
FIGS. 21A-28 depict various views of downhole drilling assemblies
with motors. FIGS. 21 and 25 depict drilling assemblies with motors
having a rotating (about its own axis) stator mounted in radial
journal bearings with a non-rotating (about its own axis) rotor,
with the rotor moving in a planetary orbital manner inside the
stator with a given eccentricity. FIGS. 21A-24 show a drilling
assembly with a solid rotor. FIGS. 25-28 show a drilling assembly
with a hollow rotor. In these configurations, when the drill bit is
off bottom, a pressure drop across the drill bit causes the hammer
to cease reciprocation while the drilling motor continues to
rotate. This provides a configuration that automatically switches
the hammer off when circulating off bottom using a splined
connection at the bit.
FIGS. 21A-24 show various views of an example of a drilling
assembly 2100 with a hammer motor 2111 usable, for example, in the
drilling system 100 of FIG. 1. The drilling assembly 2100 has a
housing 2115, the hammer motor 2111, a stator adapter 2116, a
hammer 2118 and a bit 2104.
As shown in FIGS. 21A and 21B, the hammer motor 2111 has a solid
rotor 2120 and a stator 2122 thereabout. The rotor 2120 may be free
to move eccentrically within the stator 2122 using, for example, a
double universal joint assembly or a flexible shaft 2121 at an
uphole end thereof. Nozzle 2123 may also be provided in the
drilling motor 2111 to increase flow capacity. Downhole thrust is
provided to the drilling assembly 2100 by the nozzle 2123 and
stator 2122.
Bearings 2125 (e.g., radial and/or thrust bearings) are provided to
support the stator 2122 in the housing 2115. The bearings may be,
for example, plain hard-metal thrust bearings. A stator thrust
bearing may also be provided to engage when the drilling assembly
2100 tool is switched off.
The rotor 2120 is supported from an uphole end by the flexible (or
u-joint) shaft 2121. As shown in FIGS. 22A and 22B, the stator 2122
has the stator adapter 2116 extending downhole therefrom. A
downhole end of an output shaft coupling of the stator adapter 2116
has a cam surface 2133a receivable by a corresponding mated cam
surface 2133b on an upper end of bit adapter 2127 of hammer 2118.
As the stator adapter 2116 rotates with drilling motor 2111, the
cam surface 2133a rotates along the mated cam surface 2133b of the
hammer 2118 and causes the hammer 2118 to reciprocate. In an
aligned position, the rotating stator adapter 2116 `bottoms out`
and impacts the upper end of the bit adapter 2127. The hammer 2118
is retracted a distance from the bit as the cam surface 2133a rides
up an inclined portion of cam surface 2133b to an uphole
position.
The shape of the cam surfaces 2133a,b may be configured to allow
the hammer 2118 to move axially back and forth in a reciprocating
pattern as the stator adapter 2116 rotates within the housing 2115.
The bit adapter 2127 extends through the hammer 2118 and connects
with the bit 2104. As the bit adapter 2127 is pushed downward by
the stator adapter 2116, the hammer 2118 `bottoms out.` Because the
bit 2104 is connected to the bit adapter 2127, the bit 2104
receives impact (e.g., direct and full) as it is splined to the
outer housing 2115. This reciprocation may be similar to that, for
example, described with respect to FIGS. 7-8.
Referring to FIGS. 23 and 24, the hammer 2118 has a hammer housing
2131 about the bit adapter 2127 and connected to the housing 2115.
The hammer housing 2131 has splines 2126 on an inner surface
thereof engageable with mated bit splines 2128 on an outer surface
of the bit 2104. The interacting splines 2126, 2128 permit the bit
to move axially within the hammer housing while preventing rotation
thereof.
The hammer impact is thereby provided on the cam surfaces 2133a,b.
As hammering takes place, the bit 2104 and the bit adapter 2127
slide down through the splines as the stator 2122 and stator
adapter 2116 move up and down.
FIGS. 25A-28 show various views of an example of a drilling
assembly 2100' with a hammer motor 2111' usable, for example, in
the drilling system 100 of FIG. 1. The drilling assembly 2100' is
the same as the drilling assembly 2100, except that the hammer
motor 2111' has a hollow rotor 2120' that permits the flow of fluid
therethrough.
At least a portion of the fluid passing through the drilling
assembly 2100' may be diverted through cavity 2119 of the hollow
rotor 2120'.
FIG. 29 is a flow chart depicting a method 2900 of drilling a
wellbore penetrating a subterranean formation. The method involves
2950 deploying a downhole tool into the subterranean formation via
a surface system. The downhole tool includes comprising a bottom
hole assembly, a drill string, and a drill bit. The method also
involves 2952 rotating a drilling assembly comprising a hammer
motor, a shaft operatively connectable to the hammer motor, a
driver operatively connectable to the shaft, and a hammer. The
driver includes a cam and a fixed guide having a guide surface
thereon. The hammer is operatively connectable to the driver and
axially movable therewith. The method also involves 2954 rotating
the cam with the shaft by passing a fluid through the hammer motor,
and 2956 hammering the bit with the hammer by engaging the guide
surface with the cam such that the cam is axially moved about the
guide surface during the rotating. The method may also involve 2958
selectively increasing pressure in the drilling assembly by
selectively restricting flow therethrough.
The hammering may also involve slidably positioning pins of the cam
about a guide channel of the guide surface, and/or slidably
engaging a cam surface of the cam along the guide surface. The
method may be performed in any order, and repeated as desired.
It will be appreciated by those skilled in the art that the
techniques disclosed herein can be implemented for
automated/autonomous applications via software configured with
algorithms to perform the desired functions. These aspects can be
implemented by programming one or more suitable general-purpose
computers having appropriate hardware. The programming may be
accomplished through the use of one or more program storage devices
readable by the processor(s) and encoding one or more programs of
instructions executable by the computer for performing the
operations described herein. The program storage device may take
the form of, e.g., one or more floppy disks; a CD ROM or other
optical disk; a read-only memory chip (ROM); and other forms of the
kind well known in the art or subsequently developed. The program
of instructions may be "object code," i.e., in binary form that is
executable more-or-less directly by the computer; in "source code"
that requires compilation or interpretation before execution; or in
some intermediate form such as partially compiled code. The precise
forms of the program storage device and of the encoding of
instructions are immaterial here. Aspects of the invention may also
be configured to perform the described functions (via appropriate
hardware/software) solely on site and/or remotely controlled via an
extended communication (e.g., wireless, internet, satellite, etc.)
network.
While the embodiments are described with reference to various
implementations and exploitations, it will be understood that these
embodiments are illustrative and that the scope of the inventive
subject matter is not limited to them. Many variations,
modifications, additions and improvements are possible. For
example, one or more drilling force assemblies may be provided with
one or more features of the various drilling assemblies herein and
connected about the drilling system.
Plural instances may be provided for components, operations or
structures described herein as a single instance. In general,
structures and functionality presented as separate components in
the exemplary configurations may be implemented as a combined
structure or component. Similarly, structures and functionality
presented as a single component may be implemented as separate
components. These and other variations, modifications, additions,
and improvements may fall within the scope of the inventive subject
matter.
* * * * *